diff --git a/libc/include/sys/vfs.h b/libc/include/sys/vfs.h
index ad859f0..18ae428 100644
--- a/libc/include/sys/vfs.h
+++ b/libc/include/sys/vfs.h
@@ -104,10 +104,10 @@
 #define XENIX_SUPER_MAGIC     0x012FF7B4
 #define XFS_SUPER_MAGIC       0x58465342
 
-int statfs(const char* __path, struct statfs* __buf);
-int statfs64(const char* __path, struct statfs64* __buf) __INTRODUCED_IN(21);
-int fstatfs(int __fd, struct statfs* __buf);
-int fstatfs64(int __fd, struct statfs64* __buf) __INTRODUCED_IN(21);
+int statfs(const char* _Nonnull __path, struct statfs* _Nonnull __buf);
+int statfs64(const char* _Nonnull __path, struct statfs64* _Nonnull __buf) __INTRODUCED_IN(21);
+int fstatfs(int __fd, struct statfs* _Nonnull __buf);
+int fstatfs64(int __fd, struct statfs64* _Nonnull __buf) __INTRODUCED_IN(21);
 
 __END_DECLS